We'll have only one Sigmascape (the tier in 4.2). The first raid tier was called Deltascape. We don't know yet what the next one will be called.

I also remember the talk about 4.6 and 4.7. If it happens we may get more than just three tiers. In that scenario we could have Sephiroth as the final boss of the third tier and Omega Prime as the final boss in the next and final tier. It may even be a stand-alone battle (like the Ultimate Coil) instead of a whole raid tier.

We can say almost for sure say that the last Sigmascape battle would indeed be against Omega prime. But Omega as a robot like entity only appeared in the original FFV and FFXII (believe it also appeared as a cameo supper boss in some remakes later on).

In FFVII, FFVIII and FX we did get an Omega, but the design was completely different from the robot like FFV version (on which our FFXIV version is based).

Then again I can remember Yoshi saying something about the possibility of a patch 4.6 and 4.7. Not sure where I picked that one up though, but if that's indeed true we would have a 4th Sigmascape as well.

Looks like Sigmascape will be FFVI-themed. I guess the last one will be VII or VIII-themed, whichever one has Omega Weapon (both I think?). I expect Omega Prime to be the final boss. I also expect to see Sephiroth as a boss at some point, but it wouldn't make sense for Kefka to be the final boss of this tier and Sephiroth not to be the final boss in the VII tier. Who knows, maybe they even deviate a bit from the pattern we had so far.

4.1 not really any big changes. The odd numbers always contain a new dungeon, trial and 24-man raid (in short). The bigger update will be 4.2 which will give the new raid tier, more dungeons and the start of the relic quest.